With the increasing demand for customized products, new requirements on production processes are set. Additive manufacturing with its tool-independent character shows great potential to replace conventional manufacturing processes. This also applies to power electronic assemblies, which are currently produced with a low variety of variants in large batches. However, high-quality processing of copper is a prerequisite for power electronics applications in order to achieve low power losses and long module lifetimes. Green high-power lasers show great potential to process pure copper powder by means of powder bed fusion using a laser-based system (PBF-LB/M) and open up new opportunities in power electronics production. PBF-LB/M not only facilitates the production of mono-material components such as load connectors or heat sinks but also provides multi-material capabilities, enabling 3D metallizations on ceramic substrates for use as power electronic circuit carriers. Therefore, parametric studies on the fabrication of copper metallizations via PBF-LB/M on alumina substrates using a 1 kW green laser have been conducted and are summarized in this paper. At first, the beam-matter interaction between preheated alumina substrates and parameterized laser radiation was analyzed. Based on the results, process parameters have been defined, which were then used for the production of copper metallizations. High temperature preheating of the ceramics was applied in order avoid delamination effects due to thermomechanical stresses during solidification. In parametric studies with respect to laser power, laser velocity and hatching distance on 500 °C preheated substrates, electrical conductivities of 30 MS/m and shear strengths of 69 MPa were obtained.
Additive Manufacturing technologies such as Laser Powder Bed Fusion (LPBF) provide several advantages compared to conventional manufacturing techniques by being cheaper, faster, more flexible and energy efficient. Therefore, they offer a huge potential for electronics packaging. Direct bonded copper substrates are a commonly used substrate technology for power electronics based on copper and alumina. This paper focuses on reflecting the state of the art in DBCtechnology by investigating the parameters different authors used in their experiments and deriving optimal settings based on these results. Furthermore, works addressing the LPBF of copper or laser-based copper processing on ceramics with and without afterward heat treatments were collected. These works were also studied and potentials, challenges as well as prospects for the LPBF-process of the adaption of the DBC-technology are presented.
This paper describes the development of suitable process parameters to ensure a reproducible, defect-free production of pure copper specimen via Laser Powder Bed Fusion (LPBF) also called Selective Laser Melting (SLM). Therefore, a set of experiments was developed and evaluated in a Design of Experiment (DoE) which finally provide an indication about ideal process parameters for melting pure copper powder at a wavelength of 1064 nm. For the experiments Cu-ETP with a copper purity of more than 99.90 % was processed with a laser power of up to 500 W resulting in a maximum density of 99.82 % and an electrical conductivity of 56.88 MS/m. Besides the development of optimal parameter combinations of laser power, laser speed and hatching distance, focusing the laser beam to a spot diameter of about 35 μm with a fused silica f-theta lens and thus high energy intensities of about 416 kW/mm2 resulted in best materials properties.
The processes of Additive Manufacturing (AM) are nowadays mostly used for mechanical and fluid components and have already made the transition from Rapid Prototyping (RP) to Rapid Manufacturing (RM). In the electronic industry however, mostly additive printing technologies are used to a large extent. This paper reveals a new process for the additive production of copper-ceramic composites using Selective Laser Melting (SLM). With this process, 3D metallizations can be produced on Al2O3 and spinel-like compounds, as known from Direct Copper Bonded (DBC) technology, can be formed by means of thermal post-treatments. Moreover, high adhesive strengths of up to 44 N/mm2, determined with shear testing, can be reached. The technology of melting copper or copper based powder on ceramic substrates can be used for example for power electronic applications for high current capabilities due to the possibility of manufacturing thick 3D metallizations without the occurrence of warpages as known from the DBC technology. In this study, extensive parameter analysis have been conducted with respect to laser power, laser velocity, hatching distance as well as focus shifting. On the other hand, the substrate temperature during the printing process was varied and post thermal treatments were applied in order to fully densify the metallization as well as form reaction layers between the ceramic-metal interface.
One of today’s megatrends in the industrial environment is additive manufacturing. Faster prototyping, customized products like hearing devices, integrated functions like heatsinks and many other opportunities are offered by this technological development. The opportunity of using different materials and build up 3-D structures is virtually infinite. Another one is the digitalization of almost any product to build up a smart world. This trend leads to a tremendously rising amount of data to be transferred from one place to another. If a wireless transmission is not possible and if the distance is over 100 m glass fiber is the fastest and most secure way for these requirements. In case of most short-range applications up to 100 m primary copper cables or circuit paths are in use because the electrical data transfer is well known. The limited bandwidth of copper asks for new inventions to meet the demands of tomorrow. Regarding both megatrends, the solution for this upcoming bottleneck could be 3-D printed photonic packages. This paper shows a new and innovative way for the customized fabricating of short-range data transmission networks. By Aerosol Jet Printing (AJP) the so called polymer optical waveguides (POW), it is possible to build up 3-D printed light guiding structures with low attenuation on almost any three-dimensional surface. The main advantages of the here presented research are high flexibility, low weight and low costs. After three years of intensive studies the most important key facts (machine settings, geometry, performance) are summarized in this publication.
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